Anchor sheet

ABSTRACT

An improved anchor sheet is described. The anchor sheet can be injection molded from polypropylene and can have a thickness of between 0.031 inches and 0.75. Such an anchor sheet can be molded with hooks and can have an attached resilient layer. Stems integral with the anchor sheet are used to form the hooks, and may be 1 mm high and 0.55 mm in diameter. The density of stems may be approximately 230 per square inch, or approximately 128,000 stems on a plate. An anchor sheet made in this way makes an excellent field of hooks when installed onto a supporting surface such as a floor. This field of hooks can take an overlying decorative covering such as pieces of loop backed carpet. When a resilient layer is attached, for example by ultrasonic welding, to the underside of the anchor sheet, between the anchor sheet and the floor, the anchor sheet can have the right degree of “give”, so that a user can experience some cushioning effect from the resilient layer below the anchor sheet, but with some level of rigidity so that the load of walking is transmitted across a larger surface and does not “dig” into the resilient layer.

FIELD OF THE INVENTION

This invention concerns improvements to an anchor sheet having hooksacross one side for use under carpets or other decorative coverings asdescribed, for example in U.S. Pat. Nos. 6,306,477 (Pacione, Oct. 23,2001), 6,298,624 (Pacione, Oct. 9, 2001), 6,395,362 (Pacione May 23,2002), and PCT/CA 00/00681 (Pacione et al.), published under WO 00/74544on Dec. 14, 2000. This application incorporates by reference thespecifications of these earlier patent documents.

BACKGROUND OF THE INVENTION

The earlier Pacione cases generally disclose an anchor sheet which canbe supplied in various shapes and sizes, with or without a pre-attacheddecorative covering. These earlier cases also describe how individualsheets can together form a contiguous mass of anchor sheet to provide afield of hooks which engage loops on the underside of an overlyingflooring, particularly carpet pieces. Such a contiguous mass can beformed by attaching the anchor sheets directly together, either byoverlapping or abutting or by the use of attachment devices aided by thebridging of neighbouring sheets by the overlying covering. Such mass canbe free floating or attached to the floor.

As discussed in the earlier Pacione cases, the current inventor hasinvented an anchor sheet (in some contexts referred to as a hook plateor a module) which, when installed, acts to tie decorative coveringtogether as a functional unit and to add mass and stability to suchunit, particularly in the case of a unit having a flexible decorativecovering such as a carpet. The anchor sheet may be substantially coveredover one side with hooks for anchoring a decorative covering. The anchorsheet itself may be attached to an underlying substrate, such as a flooror wall, or it may be loose laid on a floor where the anchor sheet mayhave sufficient mass to prevent movement of the anchor sheet.

SUMMARY OF THE INVENTION

The present invention provides an improved anchor sheet having desirablecharacteristics when in place under a floor covering.

It is possible, generally even preferred, when using coverings incombination with the anchor sheet of the present invention to use afloor covering that includes little or no cushion layer as is oftenprovided in carpet by a foam layer, e.g., as by urethane foam. Thebenefits of an anchor sheet of the present invention are most evidentwhen it is used in combination with such a covering having little or nodistinct cushioning layer in the covering.

An anchor sheet of the present invention provides an overlying plasticsheet and an underlying cushioning layer. An anchor sheet made up of atop plastic layer and underlying cushion has been generally previouslydescribed, as in U.S. Pat. Nos. 6,298,624, 6,306,477, and 6,395,362 andWO 00/74544.

In a broad aspect, the invention is an anchor sheet made up of a plasticsheet and an underlying resilient layer secured thereto. The plasticsheet has a thickness of between 1/16 inches and ¼ inches and having aflexural modulus (ASTM D790) of between 700 and 3600 MPa. The resilientlayer has a compression force deflection (ASTM D3574-C) that is withinabout 30 percent of the compression force deflection of a low densitypolyethylene layer ⅜ thick and a density of 30 kg/m³. A value withinabout 30 percent of the compression force deflection of the indicatedmaterial can be up to 30 percent more than the value measured for theindicated material or down to 30 percent less than the value measured

When included as part of a carpet installation having an overlyingcarpet having no rubber or urethane foam layer, for example, an anchorsheet of the present invention provides a desirable “feel” or “give” asa person walks over the installation. With the present invention, acarpet having little or no internal resilient layer or cushion can beused, resulting in less stress on the carpet fibers and primary backing.The anchor sheet can also provide the required level of sturdiness sothat furniture can be placed on or moved over the installation and isrelatively resistant to puncture, under normal wear. The lower layerincludes a suitable level of resiliency for installation atop, forexample, a concrete floor of a newly constructed office building tosuitably ride over imperfections therein.

Related to the invention(s) disclosed herein are invention(s) in thefollowing U.S. provisional patent applications, all filed concurrentlyherewith and incorporated by reference:

-   -   U.S. Provisional Patent Application entitled “Carpet tile,        installation, and methods of manufacture and installation        thereof”. This application shows coverings that can be used with        an anchor sheet of the present invention;    -   U.S. Provisional Patent Application entitled “System and methods        of manufacturing hook-plates”. This application shows a method        for manufacturing an upper plastic layer that can be used as the        upper portion of the present invention;    -   U.S. Provisional Patent Application entitled “Ultrasonic welding        of resilient layers to plates”. This application shows a method        for securing a cushioning layer of the present invention to the        upper plastic layer;    -   U.S. Provisional Patent Application entitled “Floor covering        having a removable decorative inlay”. This application shows a        particular covering arrangement that can be used with the        present invention; and    -   U.S. Provisional Patent Application entitled “Anchor sheet        positioning and connection system”. This application shows ways        and means for connecting anchor sheets to each other.

In a further aspect of the invention the sheet has a resilient layermade from low-density polyethylene.

If polypropylene is used for the anchor sheet and with a resilient layermade of low-density polyethylene, the preferred thickness of the anchorsheet is about 0.125 inches. Further experimentation has shown thepreferred size of the anchor sheet and the preferred way of connectingthe anchor sheets together is as follows. It has been found that onesize of anchor sheet of approximately 24″×24″ square (taking intoaccount some possible geometric variation along the edges, usually thecorners, to accommodate devices for attaching neighboring sheets to eachother) is preferred with an overlap/underlap area provided betweenadjacent sheets, so that the sheets overlap to form a planar surface.However, with a connector disclosed in the above-detailed applicationentitled “Anchor sheet positioning and connection system”, no connectionof the sheets to the floor, or directly to each other at the overlaparea, is necessarily required.

Other additional features of the preferred anchor sheet are additionalaspects of the invention disclosed herein and are described below andoutlined in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further understood from the followingdetailed description of an embodiment of the invention, with referenceto the drawings in which:

FIG. 1 shows an anchor sheet in simplified form with an underpadaccording to this invention:

FIG. 2 shows an anchor sheet in plan view having overlapping edges inaddition to the cutaway portions for the cornerpieces;

FIG. 3 shows a cornerpiece to be used with certain geometric shapes ofanchor sheets;

FIG. 4 shows an embodiment with two differently configured anchorsheets;

FIG. 4 a shows another embodiment with two differently configured anchorsheets;

FIG. 4 b is a section through line 4 b-4 b of FIG. 4 a;

FIG. 5 is a section through line 5-5 of FIG. 4;

FIG. 6 is a section through line 6-6 of FIG. 4; and

FIG. 7 shows an embodiment of an interlocking anchor sheet.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, an anchor sheet 1 is provided. Anchor sheet 1 isplaced on or attached to a surface such as floor (not shown). In thepresent embodiment, anchor sheet 1 is in the shape of a square. Anchorsheet 1 may alternatively be configured in any shape that can beconveniently abutted with another piece to create a floor pattern suchas, for instance, a rectangle, a hexagon or an octagon or a mixturethereof. Generally, the preferred shape will be an equilateral polygon,but a rectangle or any other shape may also be used as appropriate.Typically, a shape will be chosen which allows a planar surface to becreated out of a single major piece. Such shape can have a countersinkalong one edge to receive an overlapped portion of an adjacent similarsheet. However, different shapes can be used, having any number of edgeareas which are countersunk from the top surface. Additional sheets canbe put into this area. In FIG. 1, anchor sheet 1 contains a top surfacelayer having hooks 4 countersunk area 7 which can be used by an overlapportion of an adjacent sheet of the same or different shape or for anattachment piece.

Anchor sheet 1 may also include a cushion or resilient layer 5, which isattached to a side of anchor sheet 1 opposite to hooks 4. Wheninstalled, resilient layer 5 is located between anchor sheet 1 and theunderlying floor. In this configuration, resilient layer 5 providesresilience to the anchor sheet when a downward force is applied thereto.Similarly, if an overlayment or cover, such a decorative covering (notshown), is attached to or supported by anchor sheet 1, then thedecorative covering will be similarly cushioned. The decorative coveringmay be a carpet overlaid on top of the anchor sheet. Resilient layer 5may also be used to add mass to anchor sheet 1 to inhibit movementthereof. Furthermore, resilient layer 5 may be manufactured to have agreater coefficient of friction with the floor than anchor sheet 1 inorder to reduce movement of resilient layer 5 (and, by connection,anchor sheet 1 and the decorative covering) relative to the floor.However, it should be emphasized that cushioning is not necessary foranchor sheet 1 to function, but such cushioning can have at least theadvantages described above, depending on the characteristics of theoverlayment and the intended use of anchor sheet 1.

The anchor sheet is relatively rigid in the sense that it is not tape orcloth like. Anchor sheet 1 can have the right degree of “give”, so thata user can experience some cushioning effect from resilient layer 5below the anchor sheet, but with some level of rigidity so that the loadof walking is transmitted across a larger surface and does not “dig”into resilient layer 5. This “give” is a product of the combination ofthe “stiffness” common of the anchor sheet and the “compressibility” ofthe resilient layer. To achieve a “feel” it is possible to have a morestiff anchor sheet and a more compressible resilient layer or it ispossible to have a less stiff anchor sheet and less compressibleresilient layer. However, all of the preferred combinations shown willwork, subject to the application and the personal preference of theuser.

Hooks 4 of top surface layer 3 attach to the loops of an overlyingcarpet (not shown). Hooks 4 can be attached to sheet 1 by any convenientmeans, but injection molding is preferred. It is possible for the hookmaterial to be a different plastic or polymer material, and even appliedas a film with adhesive, since hooks 4 may need to be relatively moreresilient and flexible than the anchor sheet 1 itself. In this case, alaminate anchor sheet 1 rather than unitary construction can be used.Hooks 4 have stems 1 mm high and 0.55 mm in diameter with a stem densityof approximately 230 stems per square inch of top surface layer 3. Theratio of stem height to diameter is preferably about 2:1, and may be asgreat as 10:1. The stem diameter may be in the general range of 0.3 toabout 0.9 mm. Stem diameters of as small as 0.1 mm have been found to beacceptable.

When the density of hooks 4 is approximately 230 per square inch,nearest-neighbour hooks are spaced about 1.8 mm from each other, and arearranged in a grid of equilateral triangles so that each hook has sixnearest neighbours. In this configuration, there are approximately128,000 stems on a 24 by 24-inch anchor sheet 1. Sheets having as manyas 330 stems per square inch may be used as well. While a single anchorsheet 1 may be installed, in the preferred embodiment, an anchor sheetsubfloor comprising two or more anchor sheets 1 is installed (asillustrated, in part, in FIG. 2).

As seen in FIG. 1, anchor sheet 1 has a thickness A. The appropriatethickness A will depend on the intended use of the anchor sheet, and mayvary with the type of overlayment to be used. The preferred thickness Awill generally not be less than 0.062 inches. One preferred thickness Ais about 0.125 inches, but the thickness A may preferably

flooring (not shown) is replaced, or where a thick anchor sheet needs tobe used to create a level surface with an adjacent surface.

The appropriate thickness of resilient layer 5 may also vary dependingon the intended use of the anchor sheet, and the type of overlayment tobe used. For many uses, the preferred thickness of resilient layer 5 maybe about 0.375 inches. A preferred total thickness when resilient layer5 is combined with an anchor sheet of thickness A, is about 0.5 inches,not including the height of hooks 4 of anchor sheet 1. When thickness Aof anchor sheet 1 is about 0.125 inches and anchor sheet 1 includesresilient layer 5 of about 0.375 inches thick, a desirable walkabilityof the anchor sheet/resilient layer combination may be achieved.

In the above-described configuration, the material costs for the anchorsheet and resilient layer may be generally less than otherconfigurations. For example, use of a thicker anchor sheet may increasecosts. More material is required to increase the thickness of the anchorsheet because it is generally more dense than the resilient layer.Conversely, an increase in the thickness of the resilient layer isgenerally less expensive, but, depending on the magnitude of theincrease, the walkability of the anchor sheet/resilient layercombination may be negatively affected. The use of the aforementionedthicknesses may also serve to achieve a level of durability of theanchor sheet/resilient layer combination without unduly increasingmanufacturing costs.

If the combined thickness of the anchor sheet and resilient layer isgreater than about 0.5 inches, the use of such anchor sheet combinationmay be limited in some installations. For example, a thicker anchorsheet and resilient layer combination may obstruct or interfere with adoor or other nearby feature when the anchor sheet is installed.

Referring again to FIG. 1, cutaway from thickness A is a countersunkarea A which

circle. When combined with similar abutting anchor sheets aligned alongsides 9 and 11, a ¾ circular cut out area is formed. A fourth anchorsheet diagonally opposite anchor sheet 1 forms a complete circle havinga circular cut out area and could have a “hole” 14, as described below.Typically, the cut-out area will be such that the width of the anchorsheet at 13 will be approximately half of the total thickness A of theanchor sheet. However, the width of the anchor sheet at 13 may be otherthan approximately half the total thickness A. In addition, there can bea second area 14 which is cut away from the corner (the apex of theangle formed by the two sides of the square). This second area 14 alsohas a geometric shape (in this example, a ¼ of a circle) so that, whencombined with other anchor sheets, the anchor sheet edges are aligned sothat their corners meet at the virtual intersection of the four corners,and a second smaller circle is formed in the completed anchor sheetstructure.

Thus, a circular cut away area 14 within a second larger circular cutout area 7 is created when four similar anchor sheets abut each other,as shown in FIG. 2. A complementary corner piece or attachment device 31can then be added which will match the shape and thickness of thereduced thickness portion and the shape and thickness of the cutawayarea (see FIG. 3). Corner piece 31 can be attached to area 7 by glue orother permanent attachment, or by detachable attachment such as pressuresensitive adhesive or a hook and loop, or post and hole type. Fasteningdevices such as hook and loop or a screw or nail may be used to attachthe corner pieces to a floor to hold the anchor sheet to the floor atonly a few discrete points by use of the corner pieces, with or withoutdirect attachment to the anchor sheets. However, it is not necessary toattach any part of the anchor sheet 1 or corner piece 31 directly to thefloor. A preferred “snap-fit” attachment system is described, amongothers. in the above-detailed application entitled “Anchor sheetpositioning and connection system”. With this form of attachmentrelative movement between anchor sheets can be achieved, although theanchor sheets are attached directly to each other. It will also beappreciated that area 7 can have any shape or size in relation to thesize of the anchor sheet and attachment piece 31 can be correspondinglybigger.

FIG. 2 shows an arrangement of anchor sheets 1 and corner pieces 31where there is a plurality of overlapping anchor sheets 111. In thisexample, anchor sheets 111 are squares. Except as noted herein, anchorsheets 1 and 111 have similar characteristics, and the description ofone generally applies to the other (e.g., materials used formanufacture). Unlike the embodiment in FIG. 1, anchor sheets 111 do notabut each other in one plane only. Rather, anchor sheets 111 have anunderlay area 15 in which there is a lower portion edge 16. Underlayarea 15 is indicated in FIG. 2 by a grid marking, but underlay area 15is part of anchor sheet 111. Underlay area 15 is configured to lie underoverlap area 19 on an adjacent sheet 111. Overlap area 19 extends on twosides of each sheet 111, and underlay area 15 extends on the other twosides. Overlap area 19 overlaps the underlay area 15 of each sheet 111,for instance, along an area 20 (the area between the top abutment edgeat the dotted line). Overlap and underlay areas 19 and 15 may beconfigured to extend from anchor sheet 111 by a similar amount. Thisenables underlay area 15 to generally support overlay area 19. However,the degree of overlap need not be complete. For example, overlap area 19may extend a fraction as far as underlay area 15. Such unmatched overlapcan affect the degree of support provided at overlap area 20. In anembodiment, each of overlap area 19 and underlay area 15 may extend fromsheet 111 by two inches, and preferably extend by one inch, to form agenerally uniform overlap thereof in area 20. The thickness of theoverlap area 19 may be approximately half the thickness of thickness A.

An area of reduced thickness 21 is formed in the general vicinity ofwhere the apex of

underlay edges 15. The cutout is centered over the area of abutment forinstance lower portion edges 16 of anchor sheets 111. The cutout is notcentred over the corner line of abutment 25 created by the overlap edgesextending over the area of overlap 19. In addition to the reducedthickness area 21 (similar to area 7 in FIG. 1) there is a cutaway area23.

It is possible to use an embodiment by providing a reduced thicknessarea along any edge (or portion of an edge) of a modular anchor sheet,having a cut away area within the reduced thickness area to provide acountersink for use with the attachment devices described. A reducedthickness area surrounding a cut away area may also be located anywherein the interior of an anchor sheet for use of an attachment device atthat interior point. However, this is generally not preferred, unlessthe attachment device is to be attached to the floor because anattachment device at an interior point can obviously not connect twoanchor sheets together.

If an overlapping arrangement is used, the extent of underlay edges 15and overlap 19 need not be along more than one side, nor need it bealong an entire side. Overlap may occur at just a portion of one sideenough to permit portions of co-operating anchor sheets 1 to overlap.Similarly, the particular shape of such overlapping pieces may be variedas long as the overlap is sufficient to achieve the functions describedherein.

In one embodiment, anchor sheets 1 are square, of similar size andshape, and have sides in the range of 24 to 48 inches, although anchorsheets outside of this range may also be used.

Anchor sheets 111 may be made of an extruded or injection moldedmaterial in which the two pieces are thermally bonded so as to form theoverlap 19 and underlay area 15. Sheets 111 may be cut by a gauge orjig. Anchor sheet modules 111 may be die cut. The layer of hooks may bethermally bonded to the surface of the top sheet. Alternatively, the

injection-molded using a one- or two-step or multi-step process mold,using materials such as polypropylene or polyethylene.

The overlap 19 and underlay 15 areas of the sheets 111 may be providedwith means for detachable or permanent attachment, or the underlay areas15 of an adjacent sheet may simply lie underneath and support theoverlap areas 19 without any form of attachment. Preferably, however,any attachment provides for relative movement between adjacent sheets.The snap fit arrangement described in the above-detailed applicationentitled “Anchor Sheet Positioning and Connection System” could besuitable. Possibly, the sheets 111 may also be made with correspondingregistering bumps and indentations (not shown) in the overlap 19 andunderlay 15 portions of sheets 111 to assist in retaining sheets 111together and in alignment during installation.

In cases where hook and loop systems or hooks are provided for, thehooks may be temporarily covered by a hard slip covering as discussed inU.S. Pat. No. 6,306,477, or a soft covering as disclosed in U.S. Pat.No. 4,822,658 to temporarily prevent premature engagement of the hooksto the loops.

Anchor sheet 111 may alternatively be configured to work in conjunctionwith one or more differently configured anchor sheets. For example, afirst type of anchor sheet (not shown) could be constructed to havecomplementary corner pieces (such as 31 in FIG. 3) attached orintegrally molded to the corners thereof. A second complementary anchorsheet, such as anchor sheet 111 would receive the corner pieces in asimilar manner as described for the preferred embodiment. Alternatively,two or more anchor sheets could be configured to have an interlockingkeystone or jigsaw puzzle like shape. An example of an interlockingkeystone anchor sheet 111′″ is illustrated in FIG. 7. If such anarrangement is used, then

thereof to inhibit separation and bending of adjacent anchor sheets awayfrom their common plane. However, the keystone male in portion 41 couldbe made smaller than the opening so that some relative movement betweenthe sheets could be possible while still being interlocked.

Referring to FIGS. 4 to 6, anchor sheets 111′ (shown in white and lightgrey) and 111″ (shown in dark grey) are different yet configured to becomplementary to one another. The shading of sheets 111′ and 111″ inFIG. 4 is done merely to distinguish the two configurations. Theseanchor sheets are arranged, positioned, or connected to one another in asimilar manner as described for the preferred embodiment. These anchorsheets differ from the preferred embodiment in that anchor sheet 111′has only an underlay areas 15′ which co-operate with overlay areas 19″of anchor sheet 111″. The dashed line in FIG. 4 shows the extent of theunderlay area 15′ of anchor sheet 111′. FIGS. 4 a and 4 b illustrates asimilar arrangement wherein anchor sheet 111′″ serves to connect anchorsheets 111′.

Referring again to FIG. 1, the thickness A is ⅛ of an inch, and thethickness of the anchor sheet at 13 is 1/16 of an inch. (Similarly, theoverall thickness of anchor sheet 111 may be ⅛ of an inch, with thethickness of the underlay area 15 being 1/16 of an inch.) The thicknessof the resilient layer 5 is in the range from approximately ¼ of an inchto ⅜ of an inch, depending on the desired resiliency and amount ofsurface traffic. Hooks 4 of top surface layer 3 have a density that mayrange from about 160 to 1200 hooks per square inch, and may be as highas 2000 hooks per square inch. The preferred density is approximately230 hooks per square inch.

The preferred materials for anchor sheet 1 and resilient layer 5 arepolypropylene and polyethylene. The preferred plastic material foranchor sheet 1 is polypropylene, such as

ExxonMobil PP7805 E2 copolymer grade for compounding or injectionmolding. Accutuf® has a melt flow index of 100, a tensile yield strengthof 4100 psi, a flexural modulus of 250×10³ psi. PP7805 E2 has a meltflow index of 80 @ T=230° C., F=2.16 kg), and a tensile strength atyield of 33 MPa (50 nm/min). Other plastics may be used such as thosesold as STAMYLAN (TM) P 112MN40, with an ISO 1873 indication of PP-H orother thermoplastic materials. Stamylan (TM) has a melt flow index of 50169 T=230° C., F=2.16 kg), a flexural modulus of 1900 MPa, proportionalstrength of 35 MPa, ultimate strain of greater than 50%, and a densityof 910 kg/m³ and a melting point of approximately 160° C. Otherpolypropylenes such as those having lower or higher melt flow indexes,for example, 80 or 100, may also be used. It will be appreciated thatother materials may also be used in the injection process, includingpolyethylene terephthalate, nylon and other polymers. In general, theplastic from which the sheet is manufactured has a flexural modulus ofbetween 1200 and 2600 MPa (ASTM D790), or a flexural modulus of between1300 and 2500 MPa, or a flexural modulus of between 1400 and 2400 MPa,or a flexural modulus of between 1500 and 2300 MPa, or a flexuralmodulus of between 1600 and 2200 MPa, or a flexural modulus of between1700 and 2100 MPa, or a flexural modulus of between 1800 and 2000 MPa.

In a preferred embodiment, resilient layer 5 is made from low densitypolyethylene with a density of approximately 30 kg/m³. Other foamshaving a suitable compression force deflection test may be used, and areof a suitable material such as polyurethane or rubber. The preferredfoam has a compression force deflection (ASTM D3574-C) which is the sameor very near to that of the disclosed polyethylene foam that is ⅜ inchesthick and has a density of 30 kg/m³.

ASTM standards referred to herein are available from ASTM International.100 Barr

ASTM D3574, Test C, is the compression force deflection test (50%compression) as set out in designation D 3574-01 on Jan. 22, 2003. Thevalue obtained in the test is that set out as the standard, i.e., 50 mmby 50 mm by 25 mm in thickness.

Flexural modulus is determined according to ASTM D790 at a temperatureof 23° C.

In alternative embodiments, anchor sheet 1 is made of thin polycarbonateor polyester. For thick covering materials such as stone or ceramic,anchor sheet 1 may be as thick as ¼ of an inch or even greater.Thickness may vary depending upon the covering material and thestability requirements for any covering such as carpet. It is alsopossible for anchor sheet 1 to be made of thin sheet metal, carbonfibres or some form of polymer.

Anchor sheets 1 may be any size convenient for sale, transportation orinstallation, typically in the range of 12 inches by 12 inches square to36 inches by 36 inches square. As noted, anchor sheet 1 is anapproximately 24 inches by 24 inches square. In an alternativeembodiment, anchor sheet 1 is an approximately 25 inches by 25 inchessquare.

Anchor sheets 1 may be manufactured using some convenient method such asthe injection moulding and coining method disclosed in theabove-detailed patent application entitled “System and Methods ofManufacturing Hook Plates”. The referenced application discloses that,in order to manufacture an anchor sheet or hook plate, injection moldingis used. The hook plate manufactured by the molding apparatus (notshown) may be a square that is 24 by 24 inches, and has ⅛ of an inchthickness. Stems integral with the hook plate are used to form thehooks, and may be 1 mm high and 0.55 mm in diameter. The density ofstems may be approximately 230 per square inch, with a distance betweenstems of 1.8 mm arranged in a regular triangle, or approximately 128,000stems on a plate.

The polypropylene material is injected into the mold at a temperature ofapproximately 280° C. and a pressure of approximately 150 bar, while themold is internally cooled to a temperature of approximately 60° C. Underthese constraints, the injection time is approximately 2 seconds, theholding time is approximately 12 seconds, the cooling time isapproximately 35 seconds, and the ejection time is approximately sixseconds, for a total cycle time of approximately 55 seconds. Due to thelarge number of small stems being molded across the plate, it isimportant that the work-piece be ejected from the mold before theshrinkage of the work-piece is sufficient to shear the stems as they sitin the array of cavities in the mold. In the molding process of thepresent description, the total holding and cooling time is approximately47 seconds, and it has been found that letting the hook plate cool forlonger than this time results in shearing of the stems from the rest ofthe hook plate under the given pressure conditions for the material.Also, with the large number of small stems being molded across theplate, it is important that the hook plate be ejected from the mold atapproximately the same time across the entire work-piece. Air ejectorsmay be used for this purpose.

Once the hook plate is removed from the mold, it is allowed to passivelycool to room temperature. This step is not necessary if the subsequentcoining parameters are adjusted to compensate. When removed from themold, the hook plate will have a surface temperature of approximately60° C.

The stems are coined into an array of mushroom-headed hooks by engaginga heated coining plate onto the tops of the array of stems, melting (orsoftening) the tops of the stems and deforming them into a mushroom-headshape. A generally planar coining plate may be engaged by lowering it touniformly apply pressure to the tops of the stems.

The coining plate is preferably made of steel, and is heatedelectrically. The contact surface of the coining plate is relativelyflat and smooth, having no substantial designed cavities therein forforming the heads.

The coining plate is heated above the melting temperature of thematerial of array of stems, and is then lowered so that the coiningsurface engages the tops of array of stems. This causes the plastic intops of array of stems to become molten and deform, creating an array ofmushroom heads or hooks.

Placed beneath the uncoined plate is a compressible resilient layer madeof any resilient material that is more resilient and compressible thanthe material of the work-piece being coined. While not essential, theresilient layer provides a cushioning effect underneath the uncoinedhook plate. Initially the downward force of the coining plate onto thestems and the heat transfer thereto is not sufficient to significantlycause the stem-heads to deform, as the resilient layer begins tocompress, until the elastic resistance of resilient layer and the heattransfer are sufficient to alter the shape of the stem heads, therebycausing the stems to form an array of hooked heads. The resilient layermay lessen any effect which might be caused by the coining surface ofthe coining plate not being parallel with the stem heads. This causesthe stems to form the heads at substantially the same time, therebyproducing generally uniform hooks for the hook plate.

Numerous modifications, variations, and adaptations may be made to theparticular embodiments of the invention described above withoutdeparting from the scope of the invention, which is defined in thefollowing claims.

1. An anchor sheet for underlying a floor covering, the sheetcomprising: (a) a plastic sheet having a thickness of between 1/16inches and ¼ inches and having a flexural modulus (ASTM D790) of between700 and 3600 MPa; and (b) a resilient layer secured to a first side ofthe plastic sheet and having a compression force deflection (ASTMD3574-C) that is within about 30 percent of the compression forcedeflection of a low density polyethylene layer ⅜ inches thick and adensity of 30 kg/m³.
 2. The anchor sheet of claim 1 wherein in theplastic sheet is an injection-molded thermoplastic.
 3. The anchor sheetof claim 1 wherein the plastic is polyethylene.
 4. The anchor sheet ofclaim 1, wherein the plastic sheet has a thickness of between about ⅛inches.
 5. The anchor sheet of claim 1, wherein a second side of theplastic sheet is covered by hooks integrally molded therewith.
 6. Theanchor sheet of claim 6, wherein the hooks having a density between 160hooks per square inch to 1200 hooks per square inch, or approximately230 hooks per square inch, or approximately 330 hooks per square inch.7. The anchor sheet of claim 1, wherein the resilient layer comprises,or consists essentially of, polyethylene.
 8. The anchor sheet of claim1, wherein the plastic sheet has a flexural modulus of between 1200 and2600 MPa, or a flexural modulus of between 1300 and 2500 MPa, or aflexural modulus of between 1400 and 2400 MPa, or a flexural modulus ofbetween 1500 and 2300 MPa, or a flexural modulus of between 1600 and2200 MPa, or a flexural modulus of between 1700 and 2100 MPa, or aflexural modulus of between 1800 and 2000 MPa.
 9. The anchor sheet ofclaim 1, wherein the anchor sheet is a square and having an outer planardimension in the range of between approximately 12 inches by 12 inchesand approximately 36 inches by 36 inches.
 10. The anchor sheet of claim9, wherein the anchor sheet is approximately 24 inches by 24 inches. 11.An anchor sheet comprising: a sheet with a first and second surface; thesheet being made of a polypropylene; hooks projecting from said firstsurface; and a resilient layer made of low density polyethylene attachedto the second surface; wherein the sheet has a thickness between 0.062inches and 0.50 inches.
 12. The anchor sheet of claim 11, wherein thesheet has a thickness of approximately 0.125 inches.
 13. The anchorsheet of claim 12, wherein the sheet is injection molded.
 14. The anchorsheet of claim 3, wherein the anchor sheet is a square in the range ofapproximately 12 inch by 12 inch to approximately 36 inch by 36 inch.15. The anchor sheet of claim 14, wherein the anchor sheet isapproximately 24 inch by 24 inch.
 16. The anchor sheet of claim 13,wherein the first surface bears a field of hooks, the hooks having adensity between 160 hooks per square inch to 1200 hooks per square inch.17. An anchor sheet shaped to have a substantially flat square lowerlayer part having an underside covered in a resilient layer and asubstantially flat square upper layer part of the same size as the lowerlayer part having an upper side substantially covered in hooks in whichthe upper layer part is offset from the lower layer part an equal amountalong two adjacent edges to expose two adjacent portions of the lowerlayer part and in which countersunk holes are formed through the anchorsheet centred on the corners formed by the lower layer part wherein, thesheet has a total thickness between 0.020 inches and 0.75 inches in itsthickest part.
 18. The anchor sheet of claim 17, wherein the sheet has athickness between 0.062 and 0.75 inches in its thickest part.
 19. Theanchor sheet of claim 18, wherein the sheet has a thickness ofapproximately 0.125 inches at its thickest.
 20. The anchor sheet ofclaim 19, wherein the sheet is injection moulded.
 21. An anchor sheetfor use in a subfloor for detachable attachment to a decorativecovering, the anchor sheet comprising: an upper surface having a meansfor detachable attachment to the decorative covering; a lower surfaceopposite the upper surface, the lower surface being covered with aresilient layer; a recess of a first shape reducing the thickness of theanchor sheet in a first area; and a complete cut through the anchorsheet of a smaller second area within the first area of a second shape;wherein the sheet has a thickness between 0.020 inches and 0.75 inches.22. The anchor sheet of claim 21, wherein the sheet has a thicknessbetween 0.062 and 0.75 inches in its thickest part.
 23. The anchor sheetof claim 22, wherein the sheet has a thickness of approximately 0.125inches at its thickest.
 24. The anchor sheet of claim 21, wherein thesheet is injection molded.
 25. An anchor sheet comprising: a sheet witha first surface and a second surface; the sheet being made of one of apolypropylene and a polyethylene, and a resilient layer attached to thesecond surface; wherein the first surface bears a field of hooks, thehooks having a density between 160 hooks per square inch to 1200 hooksper square inch.
 26. The anchor sheet of claim 25, wherein the field ofhooks has a density of approximately 330 hooks per square inch.
 27. Theanchor sheet of claim 25, wherein the anchor sheet is a square in therange of approximately 12 inch by 12 inch to approximately 36 inch by 36inch.
 28. The anchor sheet of claim 27, wherein the resilient layer hasa thickness between ¼ of an inch and ⅜ of an inch.
 29. The anchor sheetof claim 28, wherein the sheet has a thickness between 0.020 inches and0.75 inches.
 30. The anchor sheet of claim 29, wherein the sheet has athickness between 0.062 inches and 0.75 inches.
 31. The anchor sheet ofclaim 30 wherein the sheet is 0.125 inches thick.
 32. An anchor sheetfor use in a subfloor for detachable attachment to a decorativecovering, the anchor sheet comprising: an upper surface having a meansfor detachable attachment to the decorative covering; a lower surfaceopposite the upper surface, the lower surface being attached to aresilient layer; one of an overlay and an underlay area located adjacentan edge of the anchor sheet, wherein the anchor sheet has a reducedthickness in the area, and the area is configured to overlap with theother of an overlay and underlay area of a complementary anchor sheet;and wherein the anchor sheet has a maximum thickness of between 0.020inches and 0.75 inches.
 33. An anchor sheet for use in a subfloor fordetachable attachment to a decorative covering, the anchor sheetcomprising: an upper surface having a means for detachable attachment tothe decorative covering; a lower surface opposite the upper surface, thelower-surface being attached to a resilient layer; and one of a male andfemale feature defined in the anchor sheet and located adjacent an edgeof the anchor sheet, the feature being configured to interlock with theother of male and female feature of a complementary anchor sheet. 34.The anchor sheet of claim 33, wherein the feature is keystone-shaped.35. The anchor sheet of claim 33, wherein the feature is jigsaw puzzlepiece-shaped.
 36. An anchor sheet comprising: a first layer of apolypropylene sheet of between 0.062 inches and 0.50 inches; and asecond layer of polyethylene foam of a density of at least 20 kg/m³ andof thickness of between ¼ inches and ⅜ inches.
 37. The anchor sheet ofclaim 36 in which the anchor sheet provides for countersunk areas atleast along one edge.